Motor vehicle comprising an internal combustion engine and an auxiliary power unit

ABSTRACT

The invention starts with a motor vehicle with an internal combustion engine ( 12 ) and an auxiliary power supply device, which includes a fuel cell ( 50 ), wherein energy flows and/or media flows of the internal combustion engine ( 12 ) and the fuel cell ( 50 ) are coupled with one another, in which a cooling and heating circuit ( 10 ) is provided. It is proposed that the cooling and heating circuit ( 10 ) features a first partial circuit ( 26 ) and a second partial circuit ( 44 ), of which the first ( 26 ) is allocated to the internal combustion engine ( 12 ) and the second ( 44 ) to the fuel cell ( 50 ), and that the two partial circuits ( 26, 44 ) are connected with one another via a supply line ( 62 ) having a supply valve ( 66 ) and via return line ( 64 ) having a return valve ( 68 ).

The invention started with a motor vehicle with an internal combustionengine and an auxiliary power supply device in accordance with thepre-characterizing clause of claim 1.

PRIOR ART

In several operating states of the motor vehicle, for example before orduring a cold start, during short-distance traffic or during long traveldown a grade, a heat yield in the cooling water via the internalcombustion engine itself is not given or is insufficient, in particularif the efficiency of the internal combustion engine is very good andconsequently there are low heat losses. Consequently, the internalcombustion engine reaches its optimal temperature in a short time orelse much later, which leads to increased fuel consumption and toincreased exhaust emissions.

In addition, in the case of low outside temperatures, considerableamounts of heat are required to de-ice the vehicle windows or to heatthe vehicle passenger compartment and therefore guarantee adequatedriving safety and good driving comfort. Currently, this problematicsituation is being solved predominantly with chemical or electricauxiliary heaters. Although chemical auxiliary heaters, e.g., burners,offer high comfort due to the possibility of heating the internalcombustion engine even at a standstill, they are relatively expensive.Electric auxiliary heaters in accordance with the principle ofresistance heating are limited in terms of performance, because not asmuch current as desired can be made available by the generator and thebattery.

A motor vehicle with an internal combustion engine and an auxiliarypower supply device, also called APU (Auxiliary Power Unit), forelectrical consumers on board the motor vehicle is known from EP 1 203697 A2, which includes a fuel cell system and a battery coupled to it.This device increases the electrical power of the motor vehicle andcreates the possibility of operating a greater number of electricconsumers independent of the operation of the internal combustionengine. The internal combustion engine and the fuel cell system areattached to a common cooling and heating circuit, in which a coolersimultaneously cools the internal combustion engine and the fuel cellsystem. This is fostered by the different peak cooling capacities thatare required for the internal combustion engine during driving operationand for the fuel cell system when the vehicle is at a standstill, e.g.,during the starting phase or when operating an independent vehicleheater.

Significantly, energy and/or media flows that are generated in theprocess are coupled with one another in that, e.g., the exhaust gas ofthe internal combustion engine is guided through a system, whichincludes a heat exchanger and/or an exhaust gas catalyzer. This systemis thermally coupled with the fuel cell system. As a result, it ispossible to preheat by means of the exhaust gas heat. During theoperation of the internal combustion engine, the fuel cell system iskept at an operating temperature and therefore is available in a shorttime with an increased energy demand. On the other hand, it can bepreheated with the waste heat of the fuel cell system of the exhaust gascatalyzer before the internal combustion engine is started so that itsharmful emissions are minimized during the starting phase. Moreover, thefuel cell system is thermally connected with an air conditioner and/oran independent vehicle heater so that the waste heat thereof can be usedto heat the passenger compartment if need be.

ADVANTAGES OF THE INVENTION

In accordance with the invention, a cooling and heating circuit featuresa first and a second partial circuit, of which the first is allocated tothe internal combustion engine and the second to the fuel cell. The twopartial circuits are connected with one another, and namely via a supplyline having a supply valve and via return line having a return valve. Inaddition to the fuel cell, a heater heat exchanger of an air conditionerfor the vehicle passenger compartment, an engine oil heat exchanger anda transmission oil heat exchanger are arranged in the second partialcircuit. Before starting the internal combustion engine at low outsidetemperatures, the second partial circuit assumes the cooling of the fuelcell. Due to a plurality of electrical consumers to be supplied instandby operation of the motor vehicle, the fuel cell is subjected to apeak load in precisely this operating state so that relatively a lot ofwaste heat generates when operating the fuel cell. This waste heat istransported via the coolant of the second partial circuit on a shortpath to an aggregate with a demand for heat, e.g., the heater heatexchanger of the air conditioner. Because of this arrangement, energy tode-ice the vehicle windows as well as to air condition the vehiclepassenger compartment is advantageously available very quickly andeffectively. In order to be able to cover a maximum demand for energyand to improve the warm start behavior of the fuel cell, an auxiliaryheater can also be expediently arranged in the second partial circuit,which also gives off heat to the coolant if need be. Due to the twopartial circuits, the different, namely lower temperature level of thefuel cell as compared to the internal combustion engine can also betaken into consideration in an advantageous manner, thereby avoidingdamage to the fuel cell from overheating.

As soon as the desired temperature of the vehicle passenger compartmentis reached or if the internal combustion engine is supposed to bestarted, a controllable valve opens another line of the second partialcircuit to the engine oil heat exchanger for the engine oil of theinternal combustion engine and to the transmission oil heat exchanger sothat these media can also be heated in a purposeful manner via thecoolant of this partial circuit. In doing so, the regulation of the heatflows is oriented in any case according to a priority demand and canalso occur via both a climate control device or via a time default of anengine control. It is known that prematurely heating the engine ortransmission oil reduces fuel consumption. In addition to saving fuel,prematurely heating the engine or transmission oil shortens the startingtime of the internal combustion engine and increases its service lifesince lower temperature fluctuations occur during the starting phase.

The engine oil heat exchanger and the transmission oil heat exchangerare connected in parallel and integrated into the second partialcircuit, wherein the supply line and the return line, which connect thefirst partial circuit with the second partial circuit, are attached tothe second partial circuit in front of or behind the oil coolers. Theinflow and outflow of the coolant in this cooling branch is alsoadjusted in terms of demand via control valves in accordance with thecorresponding defaults of the climate control and/or internal combustionengine control. Thus, in the case of an increased demand for coolingpower, e.g., in driving operation, the engine oil heat exchanger and thetransmission oil heat exchanger are supplied with coolant from thepartial circuit of the internal combustion engine via the opening of thevalves in the supply and return lines, while before and during startingthe internal combustion engine, it is primarily coolant from the fuelcell and/or the auxiliary heater that flows through them for preheating.Even in this case, the heat yield is transported to the coolant eitherat needed locations or given off to the environment via a coolerattached in this partial circuit. =p The lubricating oil of the internalcombustion engine and the transmission oil are each conveyed to theengine oil heat exchanger or the transmission oil heat exchanger via anelectrically driven pump. In addition, an electrically driven auxiliarypump is arranged in the second partial circuit to convey the coolant.Since these pumps can be operated in standby operation independent ofthe internal combustion engine via the motor vehicle's onboard network,their use advantageously facilitates the preheating of both the engineand transmission oil as well as the internal combustion engine and thetransmission itself before starting. Because of the lower viscosity ofthe heated oil, starting the internal combustion engine, particularly atlow ambient temperatures, is improved, even if the temperature of theinternal combustion engine is raised only insignificantly. In order tobe able to heat the vehicle passenger compartment at the same time, thecoolant flow of the heater heat exchanger is also regulated via a heatervalve than can be triggered electrically.

When using de-ionized water, which is currently used preferentially as acoolant for fuel cells due to its property of non-conductivity, thecooling system of the fuel cell is embodied as a closed system in thesecond partial circuit. In this embodiment, along with the fuel cell andan auxiliary pump, it features special intermediate heat exchangers,which are responsible for de-coupling the different cooling media andmust be designed in stainless steel due to the material compatibilitywith de-ionized water. The engine oil heat exchanger, the transmissionoil heat exchanger and the heater heat exchanger can be manufactured ofconventional materials. The special intermediate heat exchangers made ofstainless steel can be advantageously arranged as desired in the enginecompartment and be linked with the various media flows that must bepreheated.

DRAWINGS

Additional advantages are yielded from the following description of thedrawings. Exemplary embodiments of the invention are depicted in thedrawings. The drawings, the description and the claims contain numerousfeatures in combination. The person skilled in the art will also observeindividual features expediently and combine them into meaningful,additional combinations.

The drawings show:

FIG. 1 A schematic representation of a cooling and heating circuit of amotor vehicle with an auxiliary power supply device

FIG. 2 A variation of FIG. 1

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An internal combustion engine 12 and a transmission 14 of a motorvehicle are attached to a first partial circuit 26 of a cooling andheating circuit 10, in which a coolant pump 24 conveys a coolant (FIG.1). The pump 24 can be driven by a controllable electric motor ormechanically by the internal combustion engine 12, if it has a device toadjust the conveying capacity. It conveys the coolant from the internalcombustion engine 12 via a first coolant path 32, a bypass line,directly back to the internal combustion engine 12 and the transmission14. Only very little heat is withdrawn from the coolant via the bypassline 32 so that the internal combustion engine 12 and the transmission14 quickly reach an optimal operating temperature. As a result, lessfuel is used with lower harmful emissions.

Provided parallel to the bypass line 32 is a second coolant path to acooler 28, which cooperates with a ventilator 30 and withdraws excessheat from the coolant. Moreover, a connection to a compensating tank 78for the coolant is arranged in the area of the cooler 28. A thermostaticvalve 34 in the bypass line 32 and a thermostatic valve 36 in thecoolant branch to the cooler 28 regulates the coolant flow to the cooler28 and/or to the bypass line 32. To do so, the valves 34 and 36, whichcan also be combined into a two-way or three-way valve, receive defaultsfrom a climate or engine control (not shown) via a signal line 38.

An electrically driven engine oil pump 16 and an electrically driventransmission oil pump 18 convey the engine oil or the transmission oilto a engine oil heat exchanger 40 or a transmission oil heat exchanger42. They can be operated independently of the internal combustion engine12 from the electrical onboard network of the motor vehicle. The oilinlets of the pumps 16, 18 and the oil heat exchangers 40, 42 aredesignated with 20 and the outlets with 22. The engine oil heatexchanger 40 and the transmission oil heat exchanger 42 are allocated toa second partial circuit 44 of the cooling and heating circuit 10, whichpreferentially takes over the cooling of a fuel cell 50. In the case ofindependent vehicle air conditioning, the fuel cell 50 supplies theonboard network of the motor vehicle in connection with a switchingelement 48. Thermal energy is generated during the operation of the fuelcell 50, which is transported via the coolant of the second partialcircuit 44 on a short path to the engine oil heat exchanger 40 and thetransmission oil heat exchanger 42. The heat exchangers 40 and 42 thentransfer the energy to the engine or transmission oil so that thesemedia can be heated before the internal combustion engine 12 is started.As a result, the starting procedure is eased and the aggregates arequickly brought to their optimum operating temperatures.

In order to make it possible to simultaneously heat the passengercompartment of the vehicle before starting the internal combustionengine 12, a heater heat exchanger 54 and a heater fan 56 are arrangedin another branch of the second partial circuit 44. The heat yield alsotakes place in this case via the coolant. If the amount of heat givenoff by the fuel cell 50 is not sufficient, an auxiliary heater 52 can beconnected temporarily via a switching element 48. If, on the other hand,the heat yield in the partial circuit 44 exceeds the demand, the excessheat can be given off to the environment via an auxiliary cooler 58 withan auxiliary ventilator 60. As a result, the second partial circuit 44can operate largely self-sufficiently in standby operation of theinternal combustion engine 10. In addition, a compensating tank 80 isprovided in the partial circuit 44 in order to balance out thetemperature-induced volume changes in the coolant. The coolant isconveyed in the partial circuit 44 independently of the internalcombustion engine 12 by means of an electrically driven auxiliary pump46, wherein the valves 70, 72 and 74 regulate the coolant flows in theindividual branches. In this case, regulation is always oriented to apriority demand, which is transmitted via a signal line 82 to the heatervalve 74 as well as to the thermostatic valves 70 and 72 via defaults ofa climate and engine control.

A supply line 62 having a supply valve 66 and a return line 64 having areturn valve 68 connect the first partial circuit 26 with the secondpartial circuit 44. Using this connection, in cases of need, e.g., whenthe motor vehicle is in driving operation, coolant from the firstpartial circuit 26 can reach the engine oil heat exchanger 40 and thetransmission oil heat exchanger 42 in order to guarantee the requiredcooling capacity just via the cooler 28 or to keep the fuel cell 50 atoperating temperature or in standby operation to preheat the internalcombustion engine 12 via the coolant and the transmission 14 via thefuel cell 50. In this case, the coolant volume flow is adjusted in termsof demand by the supply valve 66 and the return valve 68.

When using de-ionized water, which is currently used preferentially as acoolant for fuel cells due to its property of non-conductivity, thecooling system 88 of the fuel cell 50 is embodied as a closed system inthe second partial circuit 44. In this embodiment, along with the fuelcell 50 and an auxiliary pump 26, it features special intermediate heatexchangers 84, 86, which are responsible for de-coupling the differentcooling media and must be designed in stainless steel due to thematerial compatibility with de-ionized water (FIG. 2). The engine oilheat exchanger 40, the transmission oil heat exchanger 42 and the heaterheat exchanger 54 can be manufactured of conventional materials. Thespecial intermediate heat exchangers 84, 86 made of stainless steel canbe advantageously arranged as desired in the engine compartment and belinked with the various media flows that must be preheated. Theintermediate heat exchanger 86 is thermally coupled with the engine oilheat exchanger 40 and the transmission oil heat exchanger 42 in order tofacilitate the preheating of the engine or transmission oil also in thisembodiment by using the waste heat being generated during the coolingprocess of the fuel cell 50. The heating of the vehicle passengercompartment before starting the internal combustion engine 12 is alsopossible in that the heater heat exchanger 54 is coupled with theintermediate heat exchanger 84, wherein a control valve 76 regulates theflow quantity and thereby determines the heat yield.

1. Motor vehicle with an internal combustion engine (12) and anauxiliary power supply device, which includes a fuel cell (50), whereinenergy flows and/or media flows of the internal combustion engine (12)and the fuel cell (50) are coupled with one another, in which a coolingand heating circuit (10) is provided, characterized in that the coolingand heating circuit (10) features a first partial circuit (26) and asecond partial circuit (44), of which the first (26) is allocated to theinternal combustion engine (12) and the second (44) to the fuel cell(50), and that the two partial circuits (26, 44) are connected with oneanother via a supply line (62) having a supply valve (66) and via returnline (64) having a return valve (68).
 2. Motor vehicle according toclaim 1, characterized in that an engine oil heat exchanger (40) for theinternal combustion engine (12) is arranged in the second partialcircuit (44), to which an electrically driven engine oil pump (16)conveys the engine oil.
 3. Motor vehicle according to claim 1,characterized in that a transmission oil heat exchanger (42) is providedin the second partial circuit (44), to which an electrical driventransmission oil pump (18) conveys transmission oil of a transmission(14).
 4. Motor vehicle according to claim 3, characterized in thatengine oil heat exchanger (40) and the transmission oil heat exchanger(42) are connected in parallel.
 5. Motor vehicle according to claim 1,characterized in that the second partial circuit (44) has anelectrically driven auxiliary pump (46), which conveys the coolantthrough the second partial circuit (44).
 6. Motor vehicle according toclaim 5, characterized in that a heater heat exchanger (54) is arrangedin the second partial circuit (44), whose flow can be regulated via aheater valve (74) that can be triggered electrically.
 7. Motor vehicleaccording to claim 1, characterized in that an auxiliary heater (52) isconnected to the second partial circuit (44).
 8. Motor vehicle accordingto claim 1, characterized in that the second partial circuit (44)includes a closed cooling system (88), which is operated with ade-ionized cooling medium and to which the fuel cell (50) and/or theauxiliary heater (52) are attached and in which the additional pump (46)is arranged, wherein the closed cooling system (88) is coupled with thecoolant circuit of the engine oil heat exchanger (40) and/or thetransmission oil heat exchanger (42) via an intermediate heat exchanger(84).
 9. Motor vehicle according to claim 8, characterized in that theheater heat exchanger (54) is allocated to the first partial circuit(26) and its coolant circuit is coupled with the closed cooling system(88) of the second partial circuit (44) via a second intermediate heartexchanger (86).
 10. Motor vehicle according to claim 3, characterized inthat the second partial circuit (44) has an electrically drivenauxiliary pump (46), which conveys the coolant through the secondpartial circuit (44).
 11. Motor vehicle according to claim 10,characterized in that a heater heat exchanger (54) is arranged in thesecond partial circuit (44), whose flow can be regulated via a heatervalve (74) that can be triggered electrically.
 12. Motor vehicleaccording to claim 3, characterized in that an auxiliary heater (52) isconnected to the second partial circuit (44).
 13. Motor vehicleaccording to claim 3, characterized in that the second partial circuit(44) includes a closed cooling system (88), which is operated with ade-ionized cooling medium and to which the fuel cell (50) and/or theauxiliary heater (52) are attached and in which the additional pump (46)is arranged, wherein the closed cooling system (88) is coupled with thecoolant circuit of the engine oil heat exchanger (40) and/or thetransmission oil heat exchanger (42) via an intermediate heat exchanger(84).
 14. Motor vehicle according to claim 13, characterized in that theheater heat exchanger (54) is allocated to the first partial circuit(26) and its coolant circuit is coupled with the closed cooling system(88) of the second partial circuit (44) via a second intermediate heartexchanger (86).
 15. Motor vehicle according to claim 5, characterized inthat an auxiliary heater (52) is connected to the second partial circuit(44).
 16. Motor vehicle according to claim 5, characterized in that thesecond partial circuit (44) includes a closed cooling system (88), whichis operated with a de-ionized cooling medium and to which the fuel cell(50) and/or the auxiliary heater (52) are attached and in which theadditional pump (46) is arranged, wherein the closed cooling system (88)is coupled with the coolant circuit of the engine oil heat exchanger(40) and/or the transmission oil heat exchanger (42) via an intermediateheat exchanger (84).
 17. Motor vehicle according to claim 16,characterized in that the heater heat exchanger (54) is allocated to thefirst partial circuit (26) and its coolant circuit is coupled with theclosed cooling system (88) of the second partial circuit (44) via asecond intermediate heart exchanger (86).
 18. Motor vehicle according toclaim 7, characterized in that the second partial circuit (44) includesa closed cooling system (88), which is operated with a de-ionizedcooling medium and to which the fuel cell (50) and/or the auxiliaryheater (52) are attached and in which the additional pump (46) isarranged, wherein the closed cooling system (88) is coupled with thecoolant circuit of the engine oil heat exchanger (40) and/or thetransmission oil heat exchanger (42) via an intermediate heat exchanger(84).
 19. Motor vehicle according to claim 18, characterized in that theheater heat exchanger (54) is allocated to the first partial circuit(26) and its coolant circuit is coupled with the closed cooling system(88) of the second partial circuit (44) via a second intermediate heartexchanger (86).
 20. Motor vehicle according to claim 2, characterized inthat a transmission oil heat exchanger (42) is provided in the secondpartial circuit (44), to which an electrical driven transmission oilpump (18) conveys transmission oil of a transmission (14).
 21. Motorvehicle according to claim 20, characterized in that the second partialcircuit (44) has an electrically driven auxiliary pump (46), whichconveys the coolant through the second partial circuit (44),characterized in that an auxiliary heater (52) is connected to thesecond partial circuit (44), and characterized in that the secondpartial circuit (44) includes a closed cooling system (88), which isoperated with a de-ionized cooling medium and to which the fuel cell(50) and/or the auxiliary heater (52) are attached and in which theadditional pump (46) is arranged, wherein the closed cooling system (88)is coupled with the coolant circuit of the engine oil heat exchanger(40) and/or the transmission oil heat exchanger (42) via an intermediateheat exchanger (84).